A sublimation type heat transfer method provides printed images by heating, with a thermal head and the like, a heat transfer sheet coated with a sublimation dye to transfer the sublimation dye to a sublimation transfer image receiver that comes into contact with the heat transfer sheet.
The dyeable resin to be used for the dyeable layer of the above-mentioned sublimation transfer image receiver mainly contains a saturated polyester, as disclosed in Japanese Patent Unexamined Publication Nos. 57-107885, 60-64899, 61-258790, 62-105689 and the like. Japanese Patent Unexamined Publication No. 3-136896 discloses an image receiver characterized by a multilayer laminate.
When a saturated polyester is used as a resin for a dyeable layer, high quality images having superior color density, tone and color reproducibility can be obtained. Inasmuch as recorded images are closely related to the dye preservation state, considerably high preservation performance has become attainable by carefully designing a resin for a dyeable layer, though still below the image preservation performance of photographs.
When compared to photographs, moreover, this construction, wherein a dye image receiving layer is formed on the surface, is inherently associated with a problem that images are disturbed by a long term preservation.
This problem can be resolved by the use of a dyeable resin having a higher preservation performance, but the dye sensitivity and printing speed decrease when the dyeable resin is used. Conventional multilayer laminates aim at improving releasing property by preventing heat-melting caused by heating with a thermal head.
In addition, a method for protecting images by, after dyeing, superimposing a transparent or semitransparent film having a heat-melt layer on a sublimation transfer image receiver and melt-adhering the heat-melt layer to the dyeable layer has been proposed (Japanese Patent Unexamined Publication Nos. 1-237193, 3-70637, 4-15118 and 4-52223).
Yet, the image durability afforded by these methods is insufficient.
It is therefore an object of the present invention to provide a protecting film for sublimation transfer image receiver, which is capable of resolving the above-mentioned problems and improving image durability while maintaining highly sensitive, high quality images for a long time.
It is another object of the present invention to provide a method for protecting images on a sublimation transfer image receiver using this film.
It is yet another object of the present invention to provide a sublimation transfer image receiver protected by an image protecting layer of said film.